Plastic flow is a form of which type of deformation in materials under stress?

• A. Elastic Deformation
• B. Brittle Fracture
• C. A form of permanent deformation where the material flows under stress
• D. Creep

Answer: (C)

Plastic flow tests your understanding of permanent deformation. When a material yields, its atoms rearrange through mechanisms like dislocation motion and glide, allowing the shape to change and not return to the original form when the load is removed. That permanent, flowing deformation is what plastic deformation describes.

Elastic deformation, in contrast, is reversible—remove the load and the material springs back. Brittle fracture isn’t about shape change but about cracking and breaking. Creep is deformation that occurs slowly over time under a sustained load (often at high temperature), not an immediate permanent flow. So the description that best fits plastic flow is: a form of permanent deformation where the material flows under stress.